[Samba] Winbind process stuck at 100% after changing use_mmap to no

[Volker Lendecke]

On Tue, Jul 05, 2016 at 08:12:59PM +0100, Alex Crow wrote:
> 
> 
> On 05/07/16 19:45, Volker Lendecke wrote:
> > On Tue, Jul 05, 2016 at 07:21:16PM +0100, Alex Crow wrote:
> >> I've set up the "DR" side of my cluster to "use mmap = no" and with
> >> "private dir" removed from the smb.conf.
> > Why do you set "use mmap = no"?
> >
> >> I have the MooseFS guys on the case as well. Should I put them in touch
> >> with you or vice/versa?
> > MooseFS should not have any business at all in tdb files. If you still
> > find tdb files used on MooseFS, you should investigate your
> > configuration and modify it such that tdb files only exist on local
> > file systems.
> >
> > Volker
> 
> There are *no* more tdb files on MooseFS, that's what I'm trying to test.

Why are you still using "use mmap = no" then?

> From the ping_pong wiki page it's instructed to use "use_mmap = no" if

As I sad in an earlier mail: The wiki page is wrong. If you don't trust
one of the primary developers of Samba and to a lesser extent ctdb
(myself, sorry for bragging) and trust the wiki more, then I am a bit
lost, sorry.

> Text here:
> 
> "
> 
> 
>     Testing mmap coherence
> 
> If you add the -m switch to ping_pong along with -rw then it will do the
> I/O coherence test via mmap. It isn't absolutely essential that a
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^
This is the key piece. It is not essential.

> cluster filesystem supports coherent mmap for CTDB/Samba, but it's nice
> for bragging points over other cluster filesystems. If your cluster
> filesystem doesn't pass this test then just use the "use mmap = no"
> option in smb.conf. Even if it does pass this test that option may be a
> good idea on most cluster filesystems."

This piece is wrong. The wiki should give you hints who wrote this.
Please contact the author of those lines, refer to the mail thread
here and ask these lines to be changed or even better -- change these
lines yourself.

> So is this documentation wrong as well? It seems to suggest setting it

Yes, the documentation is wrong.

> anyway, which is clearly not working for us (and now for sure there is
> no involvement with TDB files as I've deleted the "private dir" in smb.conf.
> 
> 
> The only reason I was asking if you'd like to talk to the MooseFS chaps
> is because of the failure of the -rw test, which as far as the
> documentation goes, seems to refer to the shared FS rather than any
> places where tdb files live.

If MooseFS does not even survive -rw without asking for mmap coherence,
just don't use it for Samba. This will eat your data for breakfast.
Gluster was there loooong ago, and they fixed it before becoming a
viable storage solution for Samba.

Volker